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Real-Time Clock
[Device Drivers]

Functions
__inline__ unsigned long	mktime (unsigned int year, unsigned int mon, unsigned int day, unsigned int hour, unsigned int min, unsigned int sec)
	Converts Gregorian date to seconds since 1970-01-01 00:00:00. Parameters: year  The year value. mon  The month value. day  The day of the month value. hour  The hours value. min  The minutes value. sec  The seconds value. Returns: Seconds since 1970-01-01 00:00:00 (UNIX timestamp).
void	time_init ()
	Initialize the Real-Time Clock.
time_t	time_read ()
	Get the seconds passed since midnight 1970-01-01 (Unix timestamp). Returns: The UNIX timestamp.

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Detailed Description

The real-time clock driver.

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Function Documentation

__inline__ unsigned long mktime (  unsigned int    year, unsigned int    mon, unsigned int    day, unsigned int    hour, unsigned int    min, unsigned int    sec )  [static]

Converts Gregorian date to seconds since 1970-01-01 00:00:00. Parameters: year  The year value. mon  The month value. day  The day of the month value. hour  The hours value. min  The minutes value. sec  The seconds value. Returns: Seconds since 1970-01-01 00:00:00 (UNIX timestamp). Assumes input in normal date format, i.e. 1980-12-31 23:59:59 => year=1980, mon=12, day=31, hour=23, min=59, sec=59. [For the Julian calendar (which was used in Russia before 1917, Britain & colonies before 1752, anywhere else before 1582, and is still in use by some communities) leave out the -year/100+year/400 terms, and add 10.] This algorithm was first published by Gauss (I think). WARNING: this function will overflow on 2106-02-07 06:28:16 on machines were long is 32-bit! (However, as time_t is signed, we will already get problems at other places on 2038-01-19 03:14:08) Thanks to Linux... (Andrea Righi). Definition at line 132 of file time.h. { if (0 >= (int) (mon -= 2)) { /* 1..12 -> 11,12,1..10 */ mon += 12; /* Puts Feb last since it has leap day */ year -= 1; } return ((( (unsigned long) (year/4 - year/100 + year/400 + 367*mon/12 + day) + year*365 - 719499 )*24 + hour /* now have hours */ )*60 + min /* now have minutes */ )*60 + sec; /* finally seconds */ }

void time_init (    )

Initialize the Real-Time Clock. Definition at line 19 of file time.c. { INIT_MUTEX(&rtc_lock); }

time_t time_read (    )

Get the seconds passed since midnight 1970-01-01 (Unix timestamp). Returns: The UNIX timestamp. Definition at line 29 of file time.c. { unsigned int year, mon, day, hour, min, sec; int i; DOWN(&rtc_lock); // When the Update-In-Progress (UIP) flag goes from 1 to 0, // // the RTC registers show the second which has precisely just // // started. // // Read RTC exactly on falling edge of update flag. // for (i=0; i<1000000 ; i++) // may take up to 1 second... // if ( CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP ) break; for (i=0 ; i<1000000 ; i++) // must try at least 2.228 ms // if ( !(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)) break; do { /* Isn't this overkill ? UIP above should guarantee consistency */ sec = CMOS_READ(RTC_SECONDS); min = CMOS_READ(RTC_MINUTES); hour = CMOS_READ(RTC_HOURS); day = CMOS_READ(RTC_DAY_OF_MONTH); mon = CMOS_READ(RTC_MONTH); year = CMOS_READ(RTC_YEAR); } while (sec != CMOS_READ(RTC_SECONDS)); if ( !(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) ) { sec = BCD2BIN( sec ); min = BCD2BIN( min ); hour = BCD2BIN( hour ); day = BCD2BIN( day ); mon = BCD2BIN( mon ); year = BCD2BIN( year ); } UP(&rtc_lock); if ( (year += 1900) < 1970 ) year += 100; return( mktime(year, mon, day, hour, min, sec) ); }

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